A second teaser image of the Mercedes-Benz Concept IAA - or Intelligent Aerodynamic Automobile - has been released, and it's now clear this is a four-door coupe with some seriously swoopy design.

Mercedes-Benz said in a release that the Concept IAA "is two cars in one: an aerodynamics world champion and a four-door coupe with embodying irresistible design".

The shadowy image does little to give away the design of this specialist show car, but what can be seen includes a sleek, double-bubbled roofline, and a sharp rear line that is reminiscent of the Volkswagen XL1.

It's apt, then, that Benz is claiming this car to be an "aerodynamics world champion", as that title currently belongs to the VW - well, at least in "production car" guise. That car's co-efficient of drag (Cd), the measure of how efficiently the car cuts through the air, is a remarkable 0.189.

The lower the number, the better. For instance, the new-generation Hyundai Sonata Hybrid has a Cd 0.24.

Mercedes-Benz “Concept IAA” (Intelligent Aerodynamic Automobile)

That this model is a four-door coupe could suggest that it offers a clue to a potential successor to the Mercedes-Benz CLS - however, what appears more likely is that this is Mercedes-Benz's rebuttal to the case of the Tesla Model S.

Benz has stated in the past that it is working on an electric vehicle with a range of 500 kilometres in an interview with Auto Motor und Sport. The company's chief of research and development, Thomas Weber, said the following when asked about an EV model:

“We are working on an intelligent concept for a highly attractive electric vehicle with a range of between 400 and 500 kilometres,” Weber replied. He added that it could be revealed “soon”.

There's also every chance the Concept IAA will bring with it some of the technology seen in the Mercedes-Benz F015 Luxury in Motion concept. That car featured an array of cameras, radar and other sensors allow it to monitor all 360 degrees of its environment and could thus drive without human control.

Stay tuned for more on the Mercedes-Benz Concept IAA.